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1MandrusiakNear-wallMeshStudyJune28,2010GEGasificationConfidentialTechnicalInformationInfluenceofNear-WallMesh•Objective–Quantifyhownear-wallmeshandboundarytreatmentaffectvelocityandturbulentkineticenergyprofiles•Approach–Simulatefully-developedturbulentflowinpipe–Differentmesharchitectures–Differentmeshresolutions–Differentwallboundarytreatments–Compareprofiles•KeyFindings–Wallboundarymeshmustmatchwallboundarycondition–Enhancedwallfunctionprovidesmostaccurateresults2MandrusiakNear-wallMeshStudyJune28,2010GEGasificationConfidentialTechnicalInformationModelDescriptionandSet-UpPeriodic100mm10mmWallAxisdP/dx=-2000Pa/m•Standardk-eturbulencemodel–Standardwallfunctions–Enhancedwallfunctions•Waterflow–Reynoldsnumber~38000•Twomesharchitecturesandthreelevelsofrefinement•Second-orderdifferencing•Steady-stateanalysis–Allresidualsconvergeto10-6–Wallshearstressnolongerchanges3MandrusiakNear-wallMeshStudyJune28,2010GEGasificationConfidentialTechnicalInformationMeshDescriptionEnhancedMeshStandardMeshMesh12X2Mesh14X4Mesh1y+1~1.25y+1~0.625y+1~0.3125y+1~125y+1~62.5y+1~31.25200cells800cells1600cells400cells1600cells6400cells4MandrusiakNear-wallMeshStudyJune28,2010GEGasificationConfidentialTechnicalInformationModelValidation–VelocityProfilesEnhancedMeshStandardMeshEnhancedWallFunctionStandardWallFunction5MandrusiakNear-wallMeshStudyJune28,2010GEGasificationConfidentialTechnicalInformationModelOutput–TKEProfilesEnhancedMeshStandardMeshEnhancedWallFunctionStandardWallFunction6MandrusiakNear-wallMeshStudyJune28,2010GEGasificationConfidentialTechnicalInformationObservationsandAssessment•Standardwallfunctionsfailwithfinenear-wallmesh–Wallshearstressoverestimated–Massflowrateunderestimated–Turbulentkineticenergyoverestimated–Near-wallvelocityprofileunderestimated•Wallmeshmustmatchwallboundarycondition–Meshrefinementproducesrelativelysmallchangesinsolutionwhenrightmeshusedwithrightboundarycondition•Standardwallfunctionproducesaccurateresults…–…aslongasthenear–wallmeshisn’ttoofineRecommendation–Enhancedwallfunctionwithenhancedwallmesh8MandrusiakNear-wallMeshStudyJune28,2010GEGasificationConfidentialTechnicalInformationModelOutput–VelocityProfilesEnhancedMeshStandardMeshEnhancedWallFunctionStandardWallFunction9MandrusiakNear-wallMeshStudyJune28,2010GEGasificationConfidentialTechnicalInformationModelOutput–EpsilonProfilesEnhancedMeshStandardMeshEnhancedWallFunctionStandardWallFunction10MandrusiakNear-wallMeshStudyJune28,2010GEGasificationConfidentialTechnicalInformationModelOutput–IntegralValues*Wallshearstressshouldbe10Paforallcases*‘Right’boundaryconditionusedon‘wrong’meshproduceserrors***MassFlowshouldbe~0.59kg/sforallcases